comma design challenge openpilot · comma four modern UI stack

Horizon Halo — confidence at a glance, headroom before the alarm

Submission by VeigaPunk · interactive prototype + design rationale · for the comma design challenge

1. Problem reframed

openpilot is L2 and already self-aware about failure likelihood and actuator saturation. Today, drivers often learn about trouble at the alert — too late for calm intervention, and the alert itself is more annoying than useful. comma four is the headlining hardware: eyes stay on the road; the UI must work in peripheral vision on a modern non-Qt stack (flat solid fills still preferred for readability in cabin light).

Design thesis: confidence is a continuous spectrum rendered as ambient geometry (halo + path fill). Actuator limits are always-on headroom meters. Sound is reserved for rate-of-change and saturation events, never for steady mid confidence.

2. Interactive comma four mock (you are the world model)

STEER

BRAKE

ACCEL

ENGAGED
HOLD

TAKE OVER — low confidence

Live controls

Model confidence 88

Steer usage 28

Brake usage 12

Accel usage 22

Speed (mph) 62

Sound: soft tick only when confidence drops across a class boundary, or when any actuator enters the top 15% of limit. No looping chime in steady amber.

Reliable Disengage < once / 10 min. Cool green halo, strong path fill, quiet headroom.

Contingent May need hands every few minutes. Amber bloom; path thins; subtle edge emphasis.

Unreliable Seconds to disengage. Red halo + toast + one short double-tick; engage ring pulses.

3. System

Horizon Halo (confidence)

Screen-edge glow + trajectory ribbon share one continuous confidence scalar c ∈ [0,1] (not three discrete LEDs). Classes are soft bands for copy/sound only:

c ≥ 0.72 → RELIABLE
0.38 ≤ c < 0.72 → CONTINGENT
c < 0.38 → UNRELIABLE

Color interpolates green→amber→red in OKLab-ish HSL (easy on any modern UI toolkit). Peripheral edges fire motion-sensitive receptors without covering the road camera plate.

Headroom meters (actuator limits)

Three always-visible bars: steer torque, brake pressure, longitudinal accel. Fill = fraction of car-specific limit currently commanded. Dashed line = soft limit (start of nonlinear tire / ABS / ESC region). Color flips amber at 70%, red at 90%.

This is the missing “pre-alert” channel: the driver sees torque climbing on a windy ramp before the classic “steering temporarily unavailable” bark.

4. Sound (alluded + implementable)

Event	One soft rising tick (120ms) on class down-transition only.
Actuator	Short double tick when any bar first crosses 85% within a 2s window.
Imminent	`c < 0.25` or multi-bar critical → one double-tick + toast; no loop until recovery then re-arm.
Non-goals	No continuous hum, no speech, no music, no per-frame beeps.

5. Mapping to openpilot signals

UI input	Suggested source
confidence `c`	Blend of model uncertainty, desire lane visibility, lead existence prob, road-edge, and historical disengage prior for scene class.
steer usage	`\|steer_torque\| / car_torque_max` (already known per fingerprint).
brake / accel	Long control output vs car accel/brake caps; include regen envelope if present.
engaged ring	Existing engaged state + soft hands-on / wheel torque presence.

6. Constraints honored

comma four first: critical state lives in periphery + lower third; center stays camera/road. Design also works on 3X mounts.
Modern flat UI (post-Qt): rectangles, solid fills, no glassmorphism, no 3D chrome — implementable in current openpilot UI stack.
Glanceable: color + edge intensity encode class without reading text; labels are secondary.
Non-intrusive: continuous amber is silent; only transitions and saturation speak.

7. Why this can beat the current board

Existing entries solve pieces well (dials, Figma systems, narrative writeups). Horizon Halo unifies the brief’s two requirements — confidence spectrum and limit proximity — into one implementable HUD for comma four with an interactive falsifiable demo, explicit signal mapping, and a sound policy that reduces annoyance (the brief’s own complaint about today’s alerts).